1 Section for Management Systems, National Institute of Aquatic Resources, Technical University of Denmark2 Department of Electrical Engineering, Technical University of Denmark3 Biomedical Engineering, Department of Electrical Engineering, Technical University of Denmark4 National Institute of Aquatic Resources, Technical University of Denmark5 Section for Population Ecology and Genetics, National Institute of Aquatic Resources, Technical University of Denmark6 Center for Fast Ultrasound Imaging, Center, Technical University of Denmark

DOI:

10.1109/ULTSYM.2012.0369

Abstract:

In the frequency range well below 1 MHz, the swimbladder is often considered the most important part for acoustic fish detection. In this work a portable system was developed to not only detect but also try to identify free-swimming fish. It has been used to measure the ultrasound backscatter at 1 MHz from fish. The system consists of a Reson TC3210 1 MHz single-element transducer, a dual-frequency, multi-beam Blueview P900-2250 sonar, and three Oregon ATC9K cameras. The Reson transducer is connected to an Olympus pulser-receiver monitored by a portable computer through a Picoscope 4226 PC oscilloscope. Exsitu experiments were performed at the NorthSea Oceanarium in Hirtshals, Denmark. The positions, orientations, and lengths of fish were estimated by three dimensional image analysis, taking the measured acoustic distance into account, while species were identified manually. These experiments indicate that at 1 MHz the surface areas (also fins and tail) of the fish can give echoes that are much stronger (up to 3 times) than the swimbladder can, therefore important for identification of fish